These types are identical, and expect a string that could be a package or module name. That's basically a bunch of identifiers stuck together with double-colons. One key quirk is that parts of the package name after the first may begin with digits.

The DistName type checks for a string like MooseX-Types-Perl, the sort of thing used to name CPAN distributions. In general, it's like the more familiar ModuleName, but with hyphens instead of double-colons.

In reality, a few distribution names may not match this pattern -- most famously, CGI.pm is the name of the distribution that contains CGI. These exceptions are few and far between, and deciding what a LaxDistName type would look like has not seemed worth it, yet.

An Identifier is something that could be used as a symbol name or other identifier (filehandle, directory handle, subroutine name, format name, or label). It's what you put after the sigil (dollar sign, at sign, percent sign) in a variable name. Generally, it's a bunch of alphanumeric characters not starting with a digit.

Although Perl identifiers may contain non-ASCII characters in some circumstances, this type does not allow it. A UnicodeIdentifier type may be added in the future.

Lax and strict version strings use the is_lax and is_strict methods from version to check if the given string would be a valid lax or strict version. version::Internals covers the details but basically: lax versions are everything you may do, and strict omit many of the usages best avoided.